Hemorrhagic disease of the newborn is attributed to the deficiency of?
**Core Concept**
Hemorrhagic disease of the newborn (HDN) is a bleeding disorder that occurs in neonates due to a deficiency of vitamin K-dependent clotting factors. This condition arises from the lack of vitamin K, a essential nutrient required for the synthesis of these crucial proteins in the liver.
**Why the Correct Answer is Right**
Vitamin K is necessary for the gamma-carboxylation of clotting factors II (prothrombin), VII, IX, and X, which are produced in the liver. Without sufficient vitamin K, these clotting factors are not properly activated, leading to impaired coagulation and increased bleeding tendency in newborns. This deficiency can be due to inadequate maternal vitamin K levels, poor placental transfer, or the newborn's own inability to synthesize vitamin K.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because vitamin C is not directly involved in the coagulation cascade or the synthesis of vitamin K-dependent clotting factors.
**Option B:** This option is incorrect because folic acid is essential for DNA synthesis and repair, but it is not directly related to the coagulation pathway or the prevention of HDN.
**Option C:** This option is incorrect because iron is crucial for hemoglobin synthesis and oxygen transport, but it is not directly involved in the synthesis of vitamin K-dependent clotting factors.
**Clinical Pearl / High-Yield Fact**
Newborns are at risk of HDN due to the low levels of vitamin K in their gut, which are not sufficient to support the synthesis of clotting factors. This risk can be mitigated by administering vitamin K to the newborn within the first hour of life.
**Correct Answer:** D. Vitamin K.